Catheter delivered inflatable balloons are utilized in a wide range of surgical procedures to dilate, obstruct, or restore patency to body vessels and organs, as well as to maintain the position of catheter delivered instruments in vivo. Such balloons are typically attached to the distal tip of a small diameter catheter tube to facilitate delivery of the balloon to a treatment site within the body. The balloon is advanced by the catheter through a body vessel while in a deflated condition until the balloon is appropriately positioned proximate the treatment site. The balloon is inflated by infusing a fluid, such as saline, a contrast media, or water, into the balloon through an inflation lumen provided in the catheter. The inflated balloon is deflated after treatment and subsequently removed from the body.
Perforated and porous catheter balloons have been proposed to deliver therapeutic agents, e.g. drugs and other medicinal agents, directly to the treatment site while concomitantly performing their primary function of dilation, obstruction, etc. The localized delivery of therapeutic agents to the treatment site can increase the effectiveness of the therapeutic agent and minimize or even negate the systemic side effects of the agent. Generally, the therapeutic agent is delivered through the wall of the catheter either through openings mechanically formed in the wall or through pores present in the material used to form the balloon. A problem common to such conventional catheter balloons is that the flow-rate and the uniform delivery of fluid, and hence the therapeutic agent, through the walls of the balloon is difficult to control. Successful delivery of the therapeutic agent to the treatment site requires the therapeutic agent to penetrate the body tissue at the treatment site to a depth sufficient for the agent to effect the treatment site without effecting healthy tissue or organs proximate the tissue site. For this reason, the flow rate of and the uniform delivery of the therapeutic agent through the walls of the balloon is important. If the flow rate is too low, the therapeutic agent can fail to properly penetrate the tissue at treatment site. If the flow rate is too high, the therapeutic agent can be delivered to areas of the body outside of the treatment area and, in some cases, elevated flow rates can result in the formation of high velocity fluid jets which can traumatize the tissue adjacent the walls of the balloon.